Method for preparing and using silicate systems to treat electrically conductive surfaces and products obtained therefrom

ABSTRACT

The disclosure relates to treating a silicate medium and using the treated medium for improving the surface of metallic or electrically conductive materials. The treated medium provides a silicate medium having a defined degree of polymerization and predetermined quantities of the desired silicate polymer. The treated silicate medium can be employed in an electroless or electrolytic process.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/465,414, filed Apr. 25, 2003, U.S. ProvisionalApplication No. 60/510,230, filed on Oct. 08, 2003 and U.S. ProvisionalApplication No. 60/528,034, filed on Dec. 09, 2003. The disclosure ofthe previously identified Provisional Applications is herebyincorporated by reference.

FIELD OF THE INVENTION

[0002] The instant invention relates to preparing silicate mediums andusing silicate mediums for modifying the surface of metals and otherelectrically conductive materials.

BACKGROUND OF THE INVENTION

[0003] Silicates have been used in electrocleaning operations to cleansteel, tin, among other surfaces. Electrocleaning is typically employedas a cleaning step prior to an electroplating operation. Usage ofsilicates for cleaning described in “Silicates As Cleaners In TheProduction of Tinplate” is described by L. J. Brown in February 1966edition of Plating; European Patent No. 00536832/EP B1(Metallgesellschaft AG); and U.S. Pat. Nos. 5,902,415, 5,352,296 and4,492,616.

[0004] Processes for electrolytically forming a protective layer or filmby using an anodic method are disclosed by U.S. Pat. No. 3,658,662(Casson, Jr. et al.), and United Kingdom Pat. No. 498,485. U.S. Pat. No.5,352,342 to Riffe, which issued on Oct. 4, 1994 and is entitled “MethodAnd Apparatus For Preventing Corrosion Of Metal Structures”, describesusing electromotive forces upon a zinc solvent containing paint. U.S.Patent Nos. 5,700,523, and 5,451,431; and German Patent No. 93115628describe processes for using alkaline meta-silicates to treat metallicsurfaces. All of the aforementioned patents, patent applications andpublications are hereby incorporated by reference.

[0005] There is a need in this art for an environmentally benign metaltreatment (e.g., substantially chromate free) that imparts corrosionresistance to metallic surfaces.

CROSS REFERENCE TO RELATED AND COMMONLY ASSIGNED PATENTS AND PATENTAPPLICATIONS

[0006] The subject matter herein is related to the following commonlyassigned patents and patent applications: U.S. Pat. Nos. 6,149,794;6,258,243; 6,153,080; 6,322,687; 6,572,756B2 and U.S. patent applicationSer. Nos. 09/816,879; 09/775,072; 09/814,641; 10/211,051; 10/211,094;10/211,029 and 10/359,402. The disclosure of the foregoing patents andpatent applications is hereby incorporated by reference.

SUMMARY OF THE INVENTION

[0007] Broadly, the instant invention relates to treating a silicatemedium and using the treated medium for improving the surface ofmetallic or electrically conductive materials. The treated silicatemedium can be employed in an electroless or electrolytic process.

[0008] By “electroless” it is meant that the treated silicate medium isused in a metal or surface treatment process wherein no current isapplied from an external source (a current may be generated in-situ dueto an interaction between the metallic surface and at least one medium).By “electrolytic” or “electrodeposition” or “electrically enhanced”, asused herein it is meant to refer to an environment created byintroducing or passing an electrical current through a silicatecontaining medium while the metallic or electrically conductive surfacecontacts the silicate medium (but not in direct contact with anelectrode). Electrolytic also means passing a current through a silicatemedium while in contact with the electrically conductive substrate (orhaving an electrically conductive surface). By “metal containing”,“metal”, or “metallic”, it is meant to refer to sheets, shaped articles,fibers, rods, particles, continuous lengths such as coil and wire,metallized surfaces or electrically conductive films, among otherconfigurations that are based upon at least one metal and alloysincluding a metal having a naturally occurring, or chemically,mechanically or thermally modified surface. Typically a naturallyoccurring surface (e.g., a passivating film), upon a metal or metallizedsurface will comprise a thin film or layer comprising at least oneoxide, hydroxides, carbonates, sulfates, chlorides, among others. Thenaturally occurring surface can be removed or modified by using theinventive process. The metal containing surface refers to a metalarticle or body as well as a non-metallic member having an adhered metalor a conductive layer. While any suitable surface can be treated by theinventive process, examples of suitable metal surfaces comprise at leastone member selected from the group consisting of galvanized surfaces,sheradized surfaces (e.g, mechanically plated), zinc, chromium, iron,steel and other iron alloys, brass, copper, nickel, tin, aluminum, lead,cadmium, magnesium, silver, barium, beryllium, calcium, strontium,cadmium, titanium, zirconium, manganese, cobalt, alloys thereof such aszinc-nickel alloys, tin-zinc alloys, zinc-cobalt alloys, zinc-ironalloys, among others.

[0009] In some cases, the metal surface has been pretreated with anothermetal or compound that can interact with the silicate medium. While anysuitable pretreatment metal or compound can be used, examples ofsuitable pretreatments comprise at least one member selected from thegroup of aluminum, copper, tin, titanium, chromium, molybdenum,tungsten, vanadium, selenium, arsenic, antimony, gold, silver, nitrates,phosphates, organic precursors thereof, among others. In some cases, thepretreating metal is delivered to the metal surface via a carriercomprising at least one member selected from the group consisting ofwater, at least one silicate (e.g., sodium silicate), solvent or waterdispersible polymers, electrically conductive polymers, among others.

[0010] If desired, the inventive process can be employed to treat anon-conductive substrate having at least one surface coated with ametal, e.g., a metallized polymeric article or sheet, ceramic materialscoated or encapsulated within a metal, among others. Examples ofmetallized polymer comprise at least one member selected from the groupof polycarbonate, acrylonitrile butadiene styrene (ABS), rubber,silicone, phenolic, nylon, PVC, polyimide, melamine, polyethylene,polyproplyene, acrylic, fluorocarbon, polysulfone, polyphenyene,polyacetate, polystyrene, epoxy, among others. Conductive surfaces canalso include carbon or graphite as well as conductive polymers(polyaniline for example).

[0011] The process of using the silicate medium is a marked improvementover conventional methods by obviating the need for solvents or solventcontaining systems to form a corrosion resistant film or layer, e.g., amineral layer. In contrast, to conventional methods the inventiveprocess can be substantially solvent free. By “substantially solventfree” it is meant that less than about 5 wt. %, and normally less thanabout 1 wt. % volatile organic compounds (V.O.C.s) are present in theelectrolytic environment. The inventive process is also a markedimprovement over conventional methods by reducing, if not eliminating,chromate and/or phosphate containing compounds (and issues attendantwith using these compounds such as waste disposal, worker exposure,among other undesirable environmental impacts). While the inventiveprocess can be employed to enhance chromated or phosphated surfaces, theinventive process can replace these surfaces with a more environmentallydesirable surface (e.g., a treating a trivalent chromate containingsurface with the inventive process). The inventive process, therefore,can be “substantially chromate free” and “substantially phosphate free”and in turn produce articles that are also substantially chromate(hexavalent and trivalent) free and substantially phosphate free. Theinventive process can also be substantially free of heavy metals such aschromium, cobalt, lead, cadmium, barium, among others. By substantiallychromate free, substantially phosphate free and substantially heavymetal free it is meant that less than 5 wt. % and normally about 0 wt. %chromates, phosphates and/or heavy metals are present in a process forproducing an article or the resultant article.

[0012] The process of using the silicate medium can provide an improvedsurface upon metallic or electrically conductive materials. The improvedsurface can comprise a first film or layer (including a colloidal layeron a metal or conductive polymer), in contact with the surface, whichmay comprise a metal silicate and a second film or layer upon the firstthat comprises at least one siliceous species (e.g., as described inPages 83-94 of R. K. Iler, “The Chemistry of Silica: Solubility,Polymerization, Colloid and Surface Properties, and Biochemistry”, JohnWiley & Sons, NY, 1979; Page 86 of Englehardt and Michel, “HighResolution Solid State NMR of Silicates and Zeolites” John Wiley & Sons,NY 1987; and Bass and Turner “Anion Distribution In Sodium SilicateSolutions. Charateristization By Si29NMR And Infrared Spectroscopies AndVapor Phase Osmometry”, Journal of Physical Chemistry B, 1997 Vol101(50), Pages 10638 to 10644; all hereby incorporated by reference). Asilica containing film or coating can then be deposited upon the mono ordisilicate film as a monomeric silica species (e.g., monomeric, dimer oroligomeric siliceous species). The silica containing film or coating mayalso include colloidal silica. The colloidal silica can be generated insitu (e.g., in an electrolytic process adjacent to the Helmholtz zone ofthe anode), or added to the silicate medium.

BRIEF SUMMARY OF THE DRAWINGS

[0013]FIG. 1 is an SEM photomicrograph illustrating a potential defectthat may be associated with the presence of hydrogen. FIG. 2 is agraphical representation of an NMR scan of a silicate medium beforebeing used to treat metal components. FIG. 3 is a graphicalrepresentation of an NMR scan of the silicate medium of FIG. 2 aftertreating metal components. FIG. 4 is a schematic drawing of a barrelapparatus for treating metal containing material in accordance with oneaspect of the invention.

DETAILED DESCRIPTION

[0014] The instant invention improves the previously disclosed processesby providing a silicate medium having a defined degree of polymerizationand predetermined quantities of the desired silicate polymer (e.g., theinstant invention can increase or decrease silicate polymerization inorder to obtain the desired concentration and type of silicate species).The inventive method comprises exposing the silicate medium to a currentsource for a time and under conditions sufficient to obtain the desireddegree and concentration of polymerized silicate (e.g., oligomersranging from monomeric [Q0] to tetramers [Q4] and colloids). Thesilicate medium can be used for improving the surface characteristics ofmetallic or electrically conductive materials. The silicate medium canbe exposed to a current source before, during or after contacting ametallic surface with the silicate medium. The degree of polymerizationor speciation can be obtained or modified by varying the pH (e.g., byincreasing the pH by adding a caustic compound such as sodium hydroxide,TMOH, among others), or, in the case of sodium silicate, by varying theratio of sodium to silicon in the medium. The degree of polymerizationor speciation can also be modified by applying a current greater thanthe over potential of water so that hydrogen and oxygen are introducedinto the silicate medium. The presence of hydrogen can increase the pHof the medium on a localized basis which in turn can cause silicadepolymerization. The pH of the medium can also be increased by adding acaustic (e.g., sodium hydroxide, TMOH, etc.) which also can cause silicadepolymerization and change the concentration of siliceous species.

[0015] The compositions and processes described in the aforementionedCross Referenced Patents And Patent Applications employ silicatecontaining mediums for improving the surface of a metal. These processesmay form a mineral-like metal disilicate upon the metal surface and asilica containing surface upon the disilicate. When a zinc surface iscontacted with the silicate medium, a metal silicate, e.g., zincsilicate layer can formed by an interaction between certain oligimers orsilicate species within the silicate medium. The silicate oligomers orsilicate speciation can range from Q0 for monomeric, Q1 for dimericsilica groups, Q2 for trimeric silica groups or species (that caninclude at anion) to Q4 for polymer. When interacting the silicatemedium with a zinc surface, a silicate medium comprising Q0 and Q1species is desirable. The instant invention can be employed in order toobtain a silicate medium having a desirable concentration of Q0 and Q1species. The type and concentration of silicate species can varydepending upon the chemistry of the surface exposed to the silicatemedium.

[0016] By treating or electrifying the silicate medium, the inventivemethod can reduce potential defects that can be associated with hydrogen(e.g., hydrogen embrittlement, cracking, non-uniform films, amongpotential defects associated with in-situ hydrogen evolution). Further,a metallic surface that is treated by the inventive process can possessimproved corrosion resistance, increased electrical resistance, heatresistance (including to molten metals), flexibility, resistance tostress crack corrosion, adhesion to sealer, paints and topcoats, amongother properties.

[0017] When a silicate medium is employed in a cathodic electrolyticprocess for treating metallic surfaces, hydrogen gas can evolve upon thesurface of the metallic surfaces while silica containing material isprecipitated. Without wishing to be bound by any theory or explanation,it is believed that hydrogen bubbles can adversely affect the depositedsilica or become trapped within the deposited silica. Referring now toFIG. 1, FIG. 1 is an SEM photomicrograph of what is believed to be ahydrogen bubble trapped within the deposited silica surface.

[0018] The instant method for treating the silicate medium can bepracticed in the absence of the metal surface to be treated within thesilicate medium. Therefore, in addition to providing a silicate mediumhaving a desirable concentration of certain silicate oligomers orspecies, the instant invention can reduce the amount of hydrogen presentin the silicate medium. While hydrogen may be undesirable in certainmetal treating operations, hydrogen can be employed in the instantinvention in order to obtain a desired silicate oligomer (e.g., monomer,dimer, etc) and concentration thereof (e.g., depolymerization of onesilicate specie into a more desirable specie).

[0019] In one aspect of the invention, the silicate medium is presentbetween or adjacent to an anode and a cathode under conditionssufficient to evolve hydrogen at the cathode and oxygen at the anode(e.g., at least equal to the overpotential of water when using anaqueous carrier). The anode and cathode can be fabricated fromdimensionally stable materials or materials that contribute desirablecompounds or elements (e.g., zinc, nickel, iron, titanium, aluminum,among others). Examples of dimensionally stable materials compriseplatinum, platinum plated niobium, platinum plated titanium, iridiumoxide, among other materials stable at a pH of about 10-14.

[0020] While the inventive process for treating the silicate medium canbe practiced in any suitable manner non-limiting examples comprisetreating the silicate in one vessel and pumping into a container forcontacting metallic surfaces, a weir wherein the silicate is treated andthen transferred to contact metallic surfaces, among other methods fortreating the silicate medium separate from the metallic surface. Ifdesired, the silicate can be treated in the same vessel as the metallicsurfaces provided that hydrogen evolved from the silicate treatment hasbeen substantially dehydrogenated or treated in order to substantiallyremove hydrogen from the medium (e.g., electrify the silicate solutionfor about 15 minutes, turn off power and then introduce metal componentsinto the treated silicate solution, or electrify the silicate solutionwhile in the presence of the metal components wherein the metalcomponents are not in direct contact with the anode or cathode).

[0021] If desired, at least one compound can be added to the silicatemedium for improving the electrical conductivity of the medium. Whileany suitable compound or mixtures thereof can be added to the medium, anexample of such a compound comprises TMOH (TMOH can also be employed asa stabilizer as described below in greater detail).

[0022] In one aspect of the invention, the silicate treatment isconducted adjacent to a metal finishing operation (e.g., a barrel,basket or rack process for treating metallic components in the silicatemedium). The silicate medium is withdrawn from a tank housing themedium, treated (e.g., electrified) in order to obtain the desiredsilicate polymerization and then reintroduced into the tank. Dependingupon the condition of the silicate medium additional silicate, water,stabilizers, among other materials can be added to the silicate mediumbefore, during or after being treated. If desired, the silicate mediumcan be filtered before, during or after treatment. Examples of suitablefiltration systems comprises fibers, plates, media, among otherfiltration techniques. One suitable filtration example comprises passingthe treated or untreated silicate medium through a media comprisingdiatomaceous earth (e.g., Auto-Vac System supplied by Alar Engineering,Mokane, Ill.).

[0023] In one aspect of the invention, waste filtrate (e.g., useddiatomaceous earth media or filtrate therefrom), or silicate medium thatis undesirable for continued usage in treating metal surfaces isemployed for buffering other metal plating wastes. After filtration,silicate medium acceptable for reuse is transported to a metal finishingtank, and unacceptable silicate medium can be employed for treatingmetal plating waste streams. That is, the silicate medium has a basic pHthat can be employed for buffering or precipitating solids from othermetal plating processes (e.g., zinc plating or chromating wastestreams). Employing the silicate medium for treating metal platingwastes reduces the overall cost of waste disposal while obtainingadditional value from the silicate medium.

[0024] In a further aspect of the invention, the metal part is treatedwhile in the silicate medium without being in direct contact with ananode or a cathode (e.g., the metal part is within the silicate mediumwhile a current is passed between an anode and a cathode within themedium). The metal part can be located between, or adjacent to the anodeand/or cathode thereby causing the metal part can become bipolar. By“bipolar” it is meant that a portion of the metal part functions as ananode or a cathode or both depending upon the relationship to the anodeand cathode within the medium. The bipolar nature of the part can varydepending upon displacement of the metal part and/or electrodes. Thespatial orientation can cause a portion of the metal part to be exposedto a cathodic environment and another portion of the same part to beexposed to an anodic environment. This environment can be created bysupplying DC or AC current to the anode and cathode.

[0025] In another aspect of the invention, the silicate medium istreated and then introduced (e.g., pumped from a silicate treatmentvessel) into a tank. Metal parts can be introduced into the tank via adip-spin basket or container having metal parts. The metal parts areexposed to the silicate medium for a time and under conditionssufficient to form the aforementioned improved silicate surface. Ifdesired, the parts within the container can be activated or cleanedprior to exposure to the treated silicate medium. After removal from thesilicate medium, the metal parts can be dried, coated with a sealer ortopcoat, among other post-treatments.

[0026] In some cases, the metal surface has been pretreated with anothermetal or compound that can interact with the silicate medium (e.g., anorganic or inorganic film or layer containing the other metal is appliedprior to contact with the silicate medium). While any suitablepretreatment metal or compound can be used, examples of suitablepretreatments comprise at least one member selected from the group ofaluminum (e.g., sodium aluminate, aluminum ammonium sulfate, aluminumfluoride, aluminum nitrate, aluminum phosphate, aluminum potassiumsulfate, aluminum tartrate, among others), copper, tin, titanium (e.g.,titanates), chromium (e.g., chromates), molybdenum (e.g, molybdates),tungsten, vanadium, selenium, arsenic, antimony, gold, silver, nitrates,phosphates (e.g., sodium ammonium phosphate), sodium acetate, sodiumd-gluconate, inorganic or organic precursors thereof, at least onedopant (described below in greater detail), among others. In some cases,the pretreating metal is delivered to the metal surface via a carriercomprising at least one member selected from the group consisting ofwater, at least one silicate (e.g., sodium silicate), solvent or waterdispersible polymers, among others. The concentration of the pretreatingmetal within the carrier (e.g., water) can vary but is normally about0.001 wt % to about 5.0 wt. % (e.g., about 0.5 wt %). If desired, thepretreating metal is dissolved in at least one acid such as HCl,muratic, nitric, among others. In one aspect of the invention, an ironor a steel surface is pretreated with a phosphate (e.g., sodiumpolyphosphate), and then exposed to the silicate medium. The time andtemperature of the pretreatment can vary depending upon the desiredresults and concentration of the metal (e.g., about 10 to about 90seconds [normally about 30 seconds] under ambient conditions).

[0027] In one aspect, the surface is pretreated with an inorganic filmor layer. The inorganic film or layer can comprise at least one of theaforementioned pretreating metals. The inorganic film or layer can beformed by any suitable process. An example of a suitable processcomprises one of the processes disclosed in the aforementionedCross-Referenced Patents And Patent Applications (e.g., a zinc or zincalloy surface is exposed to an electrolytic silicate medium and then bythe inventive process). Another example of a suitable process comprisesforming a film or layer by contact with a potassium silicate containingsolution.

[0028] Without wishing to be bound by any theory or explanation, it isbelieved that the film or layer formed by pretreating the surface caninteract with the silicate medium (e.g., by ion exchanging). That is, itis believed that the film or layer can comprise metal species capable ofion exchange with the silicate medium (e.g., sodium silicate withzincate balanced sodium to form silica films/colloids).

[0029] The silicate medium can comprise water and at least one watersoluble silicate such as at least one member selected from the group ofsodium silicate, potassium silicate, lithium silicate, ammoniumsilicate, tetramethylammonium silicates, tetraakylammonium silicates,tetrabutylammonium silicates, among other silicates, siliceous speciessuch as monomeric silica, oligomeric silica, polymeric silica, colloidalsilica, among other water silicates and combinations thereof. While anysuitable silicate can be employed, an example of suitable silicatecomprises an oligomeric sodium silicate (e.g., available commerciallyfrom PQ Corporation as “D” grade sodium silicate). The oligomeric sodiumsilicate has a ratio of SiO2 wt./Na2Owt of about 2.00 wherein the amountof NaOw/w % is about 13 to about 15 (e.g., about 14.7+−0.15) and theamount of SiO2w/wt % is about 28 to about 30 (e.g., about 29.4). Theamount of at least one water soluble silicate normally comprises about 1to about 30 wt. % of the first medium. If present in the silicatemedium, the siliceous species (e.g,. colloidal silica, monomeric oroligomeric silica-containing species) can have any suitable size and,normally, range from about 10 to 200 nanometers (e.g., about 15 to about90 nm). The silicate medium has a pH of about 10 to 14 (e.g., about11.5).

[0030] In one aspect of the invention, a commercially available sodiumsilicate (N Grade sodium silicate which has SiO2 wt/Na2Owt ratio of 3:22and a lower viscosity relative to oligomeric silicate [D-Grade]) iscombined with D-grade sodium silicate in order to obtain the silicatemedium. A blend of N-Grade and D-Grade sodium silicate can be employedto tailor the pH, degree and range of silicate polymerization, cost,among other parameters of the inventive silicate medium. The addition ofat least one stabilizer such as TMOH (e.g., about 25 wt. % to eitherN-grade or D-grade sodium silicate or mixtures thereof) can change theSiO2: alkali ratio of the medium thereby enhancing condensation ofsilica species onto a metal surface (e.g., a non-amphortic metalsurface).

[0031] The silicate medium can further comprise at least one stabilizer.The stabilizer is employed for controlling or inhibiting growth ofcolloidal silica. Without wishing to be bound by any theory orexplanation it is believed that dimer, trimer and other oligomeric formspresent in the silicate medium can agglomerate or grow into colloidalsilica. The stabilizer inhibits colloidal growth thereby maintaining thedesired silicate polymerization within the silicate medium. While anysuitable stabilizer can be employed, examples of such stabilizerscomprise at least one member selected from the group oftetraalkylammonium hydroxides such as tetramethyl, tetraethyl,tetrapropyl and tetrabutyl ammonium hydroxides. The amount of stabilizercan vary depending upon the composition of the stabilizer, condition ofsilicate medium to which stabilizer is introduced, among otherparameters (e.g,. about 1% to 50 wt. % stabilizer). A non-limitingexample of a stabilized silicate medium comprises a blend of 4.78 galH2O, 2.58 gal sodium silicate (N-Grade sodium silicate), and 2.24 galtetramethylammonium hydroxide (TMAOH).

[0032] The specific electrolytic parameters used within the silicatemedium depend upon the composition of the medium, extent to which themedium has been used for treating metallic materials, time, temperature,flow rate, among other parameters. Normally, the temperature of themedium ranges from about 25 to about 95 C (e.g., about 75C), the voltagefrom about 6 to 24 volts, with a silicate solution concentration fromabout 1 to about 15 wt. % silicate (e.g., about 10 wt. % sodiumsilicate), the current density ranges from about 0.025A/in2 and greaterthan 0.60A/in2 and typically about 0.04A/in2 (e.g., about 180 to about200 mA/cm2 and normally about 192 mA/cm2), contact time with the firstmedium from about 10 seconds to about 50 minutes and normally about 1 toabout 15 minutes, and anode to cathode surface area ratio of about 0.5:1to about 2:1 (e.g., 1:1). Depending upon whether a bipolar medium isdesired, DC or AC current can be supplied to the silicate medium.

[0033] In an aspect of the invention, the silicate medium can bemodified to include at least one dopant material (e.g., to improvecorrosion resistance, reduce torque tension, increase heat resistance,among other chemical and physical properties). Dopants can be addedbefore, during or after treatment in accordance with the instantinvention (e.g., the previously described metal pretreatment). Thedopants can be useful for building additional thickness of the film orlayer obtained when exposing metallic articles to the silicate medium.The amount of dopant can vary depending upon the properties of thedopant and desired results. Typically, the amount of dopant will rangefrom about 0.001 wt. % to about 5 wt. % (or greater so long as thedeposition rate is not adversely affected). Examples of suitable dopantscomprise at least one member selected from the group of water solublesalts, oxides and precursors of tungsten, molybdenum, titanium(titatantes), zircon, vanadium, phosphorus, aluminum (aluminates), iron(e.g., iron chloride), boron (borates), bismuth, gallium, tellurium,germanium, antimony, niobium (also known as columbium), magnesium andmanganese, sulfur, zirconium (zirconates) mixtures thereof, amongothers, and usually, salts and oxides of aluminum and iron, and otherwater soluble or dispersible monovalent species. The dopant can compriseat least one of molybdenic acid, fluorotitanic acid and salts thereofsuch as titanium hydrofluoride, ammonium fluorotitanate, ammoniumfluorosilicate and sodium fluorotitanate; fluorozirconic acid and saltsthereof such as H₂ZrF₆, (NH₄)₂ZrF₆ and Na₂ZrF₆; among others.Alternatively, dopants can comprise at least one substantially waterinsoluble material such as electropheritic transportable polymers, PTFE,boron nitride, silicon carbide, silicon nitride, aluminum nitride,titanium carbide, diamond, titanium diboride, tungsten carbide, metaloxides such as cerium oxide, powdered metals and metallic precursorssuch as zinc, among others.

[0034] The aforementioned dopants can also be employed for modifying thechemistry of the silicate medium and/or physical properties of thesilicate film or layer formed on the metallic surface, as a diluent forthe medium, among others. Additional examples of such dopants are ironsalts (ferrous chloride, sulfate, nitrate), aluminum fluoride,fluorosilicates (e.g., K2SiF6), fluoroaluminates (e.g., potassiumfluoroaluminate such as K2AlF5-H2O), mixtures thereof, among othersources of metals and halogens. The dopant materials can be introducedto the metal surface in pretreatment steps and/or post treatment steps(described below in greater detail), and/or by alternating exposing themetal surface to solutions of dopants and solutions of the silicatemedium.

[0035] The silicate medium can also be modified by adding at least onediluent. Similar to the dopant, the diluent can be added before, duringor after treating the silicate medium in accordance with the instantinvention. Examples of suitable diluent comprise at least one memberselected from the group of sodium sulphate, surfactants, de-foamers,colorants/dyes, conductivity modifiers, among others. The diluent (e.g.,sodium sulfate) can be employed for reducing the affects of contaminantsentering the medium, reducing bath foam, among others. When the diluentis employed as a defoamer, the amount normally comprises less than about5 wt. % of the medium, e.g., about 1 to about 2 wt. %.

[0036] In one aspect of the invention, exposing metallic materials tothe treated silicate medium of the invention is preceded and/or followedby procedures known in this art such as cleaning or rinsing, e.g.,immersion/spray within the treatment, sonic cleaning, doublecounter-current cascading flow; alkali or acid treatments, among othertreatments. By employing a suitable post- or pre-treatment thesolubility, corrosion resistance (e.g., reduced white rust formationwhen treating zinc containing surfaces), sealer and/or topcoat adhesion,among other properties of treated metallic surface formed by theinventive method can be improved. If desired, the post-treated surfacecan be sealed, rinsed and/or topcoated, e.g., silane, epoxy, latex,fluoropolymer, acrylic, among other coatings.

[0037] In one aspect of the invention, a pre-treatment comprisesexposing the metallic surface or substrate to be treated to at least oneof an acid, oxidizer, a basic solution (e.g., potassium or sodiumhydroxide) among other compounds. The pre-treatment can be employed forremoving excess oxides or scale, equipotentialize the surface forsubsequent mineralization treatments, hydroxylize, convert the surfaceinto a silicate containing or silica containing precursor, among otherbenefits. Conventional methods for acid cleaning metal surfaces aredescribed in ASM, Vol. 5, Surface Engineering (1994), and U.S. Pat. No.6,096,650; hereby incorporated by reference.

[0038] In another aspect of the invention, the metal surface ispre-treated or cleaned electrolytically by being exposed to an anodicenvironment. That is, the metal surface is exposed to the medium whereinthe metal surface is the anode and a current is introduced into themedium. If desired, anodic cleaning can occur within the silicatemedium. By using the metal as the anode in a DC cell and maintaining acurrent of about 10A/ft2 to about 150A/ft2, the process can generateoxygen gas. The oxygen gas agitates the surface of the workpiece whileoxidizing the substrate's surface. The surface can also be agitatedmechanically by using conventional vibrating equipment. If desired, theamount of oxygen or other gas present during formation of the minerallayer can be increased by physically introducing such gas, e.g.,bubbling, pumping, among other means for adding gases.

[0039] In a further aspect of the invention, the metal part ispretreated to have a darkened appearance. The darkened part can betreated in accordance with the instant invention (e.g., exposure to asilicate medium and/or bipolar environment). The darkened part, whichhas been exposed to the instant silicate medium, provides a desirablesurface for secondary coatings; especially for dark or black secondarycoatings (e.g., cathodic lacquers such as those commercially availablefrom PPG). Examples of suitable darkening processes comprise exposingthe metal surface to a dye, anodizing, chemical reactants (e.g.,molybdate compounds), among other process effective at causing the metalsurface to have a relatively dark surface. A suitable anodizing processis described in “Zinc Anodizing” by Wolfgang Paatsch, June 1995-MetalFinishing; hereby incorporated by reference. Commercial darkeningcompounds are available from Jost Chemicalas Insta-Blak Z360. In mostcases it is desirable to pre-treat or clean the parts prior to thedarkening process (e.g., by immersion with dilute nitric acid, ammoniumcitrate, citric acid, among others). While any darkening process can beemployed, one example comprises exposing a zinc containing part to anelectrolyte comprising 20 g/L NaOH and 5 g/L NaClO2 and applying an ACcurrent having a current density of about 40A/dm2. The electrolyte ismaintained at a temperature of about 30C and the process operated forabout 40 minutes. The darkened and silicate treated parts can be driedat a temperature and time sufficient to remove water (e.g., for about 4minutes at 120C). Without wishing to be bound by any theory orexplanation, it is believed that combining a darkening process withexposure to the silicate medium can form a zinc chloride phase (e.g.,ZnCl2-4Zn(OH)2) that in turn imparts improved corrosion resistance.

[0040] If desired, the method for treating metallic materials caninclude a thermal post-treatment following exposure to the silicatemedium. The metal surface can be removed from the medium, dried (e.g.,at about 120 to about 150C for about 2.5 to about 10 minutes), rinsed indeionized water and then dried. The dried surface may be processedfurther as desired; e.g. contacted with a sealer, rinse or topcoat.Typically the amount of heating in drying steps herein is sufficient toconsolidate or densify the inventive surface without adversely affectingthe physical properties of the underlying metal substrate. Heating canoccur under atmospheric conditions, within a nitrogen containingenvironment, among other gases. Alternatively, heating can occur in avacuum. The surface may be heated to any temperature within thestability limits of the surface coating and the surface material.Typically, surfaces are heated from about 75° C. to about 250° C., moretypically from about 120° C. to about 200° C. If desired, the heattreated component can be rinsed in water to remove any residual watersoluble species and then dried again (e.g., dried at a temperature andtime sufficient to remove rinse water).

[0041] In one aspect of the invention, a post treatment followingexposure to the treated silicate medium comprises exposing the substrateto a source comprising at least one acid source or precursors thereof.Examples of suitable acid sources comprise at least one member chosenfrom the group of phosphoric acid, hydrochloric acid, molybdic acid,silicic acid, acetic acid, citric acid, nitric acid, hydroxylsubstituted carboxylic acid, glycolic acid, lactic acid, malic acid,tartaric acid, ammonium hydrogen citrate, ammonium bifluoride, fluoboricacid, fluorosilicic acid, glacial acetic acid, among other acid sourceseffective at improving at least one property of the treated metalsurface. The pH of the acid post treatment may be modified by employingat least one member selected from the group consisting of ammoniumcitrate dibasic (available commercially as Citrosol® #503 andMultiprep®), fluoride salts such as ammonium bifluoride, fluoboric acid,fluorosilicic acid, among others. The acid post treatment can serve toactivate the surface thereby improving the effectiveness of rinses,sealers and/or topcoatings (e.g., surface activation prior to contactingwith a sealer can improve cohesion between the surface and the sealerthereby improving the corrosion resistance of the treated substrate).The acid post treatment can also function to reduce any adverseinteraction between the treated surface and an overlying sealer orcoating that is sensitive to a basic pH. Normally, the acid source willbe water soluble and employed in amounts of up to about 15 wt. % andtypically, about 1 to about 5 wt. % and have a pH of less than about5.5.

[0042] If desired, after contacting the silicate medium the surface canbe rinsed; typically after being dried. By “rinse” it is meant that anarticle or a treated surface is sprayed, dipped, immersed or other wiseexposed to the rinse in order to affect the properties of the treatedsurface. For example, a surface treated by the inventive process isimmersed in a bath comprising at least one rinse. In some cases, therinse can interact or react with at least a portion of the treatedsurface. Further the rinsed surfaced can be modified by multiple rinses,heating, topcoating, adding dyes, lubricants and waxes, among otherprocesses. Examples of suitable compounds for use in rinses comprise atleast one member selected from the group of titanates, titaniumchloride, tin chloride, zirconates, zirconium acetate, zirconiumoxychloride, fluorides such as calcium fluoride, tin fluoride, titaniumfluoride, zirconium fluoride; coppurous compounds, ammoniumfluorosilicate, metal treated silicas (e.g., Ludox® products such asLudox® CL), nitrates such as aluminum nitrate; sulphates such asmagnesium sulphate, sodium sulphate, zinc sulphate, and copper sulphate;lithium compounds such as lithium acetate, lithium bicarbonate, lithiumcitrate, lithium metaborate, lithium vanadate, lithium tungstate,silanes, among others. The rinse can further comprise at least oneorganic compound such as vinyl acrylics, fluorosurfactancts,polyethylene wax, among others. One specific rinse comprises water,water dispersible urethane, and at least one silicate, e.g., refer tocommonly assigned U.S. Pat. No. 5,871,668; hereby incorporated byreference. While the rinse can be employed neat, normally the rinse willbe dissolved, diluted or dispersed within another medium such as water,organic solvents, among others. While the amount of rinse employeddepends upon the desired results, normally the rinse comprises about 0.1wt % to about 50 wt. % of the rinse medium. The rinse can be employed asmultiple applications and, if desired, heated. Moreover, theaforementioned rinses can be modified by incorporating at least onedopant, e.g. the aforementioned dopants. The dopant can employed forinteracting or reacting with the treated surface. If desired, the dopantcan be dispersed in a suitable medium such as water and employed as arinse.

[0043] In one aspect, a post-treatment comprises exposing the treatedsurface to at least one compound that absorbs, adsorbs or chemicallyremoves water from the treated surface. While any suitable compound ormethod can be employed, an example comprises rinsing the treated surfacewith at least one silane containing solution. Water can be removed fromthe treated surface, in the case of barrel processed parts, by spinningthe parts, rinsing in a silane containing solution and spinning again.

[0044] If desired, after an optional rinsing step at least one secondarycoating can be applied. Examples of suitable such coatings comprise atleast one member selected from the group of Aqualac® (urethanecontaining aqueous solution), W86®, W87®, B37®, T01®, E10®, B17, B18among others (a heat cured coating supplied by the Magni® Group),JS2030S (sodium silicate containing rinse supplied by MacDermidIncorporated), JS2040I (a molybdenum containing rinse also supplied byMacDermid Incorporated), EnSeal® C-23 (an acrylic based coating suppliedby Enthone), EnSeal® C-26, Enthone® C-40 (a pigmented coating suppliedEnthone), Microseal®, Paraclene® 99 (a chromate containing rinse),EcoTri® (a silicate/polymer rinse), MCI Plus OS (supplied by MetalCoatings International), silanes (e.g., at least one of Dow CorningZ-6040Z6137 and QP8-5314, and Gelest SIA 0610.0),tetra-ortho-ethyl-silicate (TEOS), bis-1,2-(triethoxysilyl) ethane(BSTE), vinyl silane or aminopropyl silane, epoxy silanes,vinyltriactosilane, alkoxysilanes, among other organo functionalsilanes), ammonium zirconyl carbonate (e.g., Bacote 20), urethanes(e.g., Agate L18), acrylic coatings (e.g., IRILAC®), e-coats (e.g., PPGPowercron), silanes including those having amine, acrylic and aliphaticepoxy functional groups, latex, urethane, epoxies, silicones, alkyds,phenoxy resins (powdered and liquid forms), radiation curable coatings(e.g., UV curable coatings), lacquer including cathodically appliedlacquers, shellac, linseed oil, torque tension modifiers (e.g., TNT15from MacDermid), commercially available coatings such as Technicaq 330,Techniseal 448 and Briteguard RP-90, among others. Coatings can besolvent or water borne systems. These coatings can be applied by usingany suitable conventional method such as immersing, dip-spin, spraying,among other methods. The secondary coatings can be cured by any suitablemethod such as UV exposure, heating, allowed to dry under ambientconditions, among other methods. An example of UV curable coating isdescribed in U.S. Pat. Nos. 6,174,932; 6,057,382; 5,759,629; 5,750,197;5,539,031; 5,498,481; 5,478,655; 5,455,080; and 5,433,976; herebyincorporated by reference. The secondary coatings can be employed forimparting a wide range of properties such as improved corrosionresistance to the underlying mineral layer, reduce torque tension, atemporary coating for shipping the treated work-piece, decorativefinish, static dissipation, electronic shielding, hydrogen and/or atomicoxygen barrier, among other utilities. The treated and coated metal,with or without the secondary coating, can be used as a finished productor a component to fabricate another article.

[0045] The thickness of the rinse, sealer and/or topcoat can range fromabout 0.00010 inch to about 0.00025 inch. The selected thickness variesdepending upon the end use of the coated article. In the case ofarticles having close dimensional tolerances, e.g., threaded fasteners,normally the thickness is less than about 0.00005 inch.

[0046] In another aspect of the invention, a metal part is exposed to asilicate medium and then coated with at least two secondary coatings. Ifdesired, the silicate medium can be operated in a bipolar environment.One example comprises exposing zinc plate parts (e.g., rivets) to abipolar silicate medium for about 3.5 minutes, drying the parts, rinsingwith water, drying, applying a first coating comprising sodium silicatewith aluminum and magnesium (e.g., available commercially from A-Brightas Briteguard RP-90), drying the first coating, applying a secondcoating comprising at least one silane (e.g., DowCorning Z6137), dryingthe second coating and applying a third coating comprising a polymer andwax composition (e.g., available commercially as MacDermid TNT). Thismultiple coating system can achieve improved corrosion resistance whenmeasuring in accordance with ASTM B-117 (e.g., greater than 200 hoursuntil appearance of white rust or zinc corrosion products).

[0047] In another aspect of the invention, the metal part is exposed toa silicate medium and then electrolytically coated. Examples ofelectrolytically coating comprise at least one of e-coats, cathodiclacquers (e.g., commercially available as PPG® Black Powerseal XL),among others. If desired, the metal part can be darkened prior toexposure to the silicate medium. That way a darkened part is providedwhich can be coated with a dark or black coating (e.g., to ensure that arelatively light colored surface is not visible through a relativelydark coating).

[0048] Exposure to the treated silicate medium of the invention canprovide a surface that improves adhesion between a treated substrate andan adhesive. Examples of adhesives comprise at least one member selectedfrom the group consisting of hot melts such as at least one memberselected from the group of polyamides, polyimides, butyls, acrylicmodified compounds, maleic anhydride modified ethyl vinyl acetates,maleic anhydride modified polyethylenes, hydroxyl terminated ethyl vinylacetates, carboxyl terminated ethyl vinyl acetates, acid terpolymerethyl vinyl acetates, ethylene acrylates, single phase systems such asdicyanimide cure epoxies, polyamide cure systems, lewis acid curesystems, polysulfides, moisture cure urethanes, two phase systems suchas epoxies, activated acrylates polysulfides, polyurethanes, amongothers. Two metal substrates having surfaces treated in accordance withthe inventive process can be joined together by using an adhesive.Alternatively one substrate having the inventive surface can be adheredto another material, e.g., joining treated metals to plastics, ceramics,glass, among other surfaces. In one specific aspect, the substratecomprises an automotive hem joint wherein the adhesive is located withinthe hem.

[0049] The inventive process can be used for treating a wide range ofmetal surfaces such as discrete components in a barrel, larger orunusual shaped components on a rack, continuous strips, among othersurfaces. For example, the inventive process can be used for treatingassemblages (e.g., welded structures such as a vehicle frame) in amethod comprising placing the assemblage onto a rack that transports theassemblage through the method. The assemblage is cleaned (e.g., with adilute acid), rinsed with water, hydroxilized by immersion within acaustic (e.g., dilute sodium hydroxide), rinsed, and immersed into theinventive silicate medium (i.e., a previously electrified silicatemedium). If desired, a coating can be applied (e.g., a sealer comprisingzinc silicate and at least one silane), upon the treated surface, andoptionally a second coating comprising an e-coat, a powder paint, amongothers, can be applied upon the first coating

EXAMPLES

[0050] The following Examples are provided to illustrate certain aspectsof the invention. These Examples shall not limit the scope of any claimsappended hereto.

Example 1

[0051] This Example illustrates the polymerized silicate species thatinteracts with a zinc metal surface. A silicate medium was used forprocessing zinc components in accordance with aforementioned U.S. patentapplication Ser. No. 09/814,641; incorporated by reference. The silicatemedium was evaluated before and after treating the zinc components inaccordance with conventional ²⁹Si nuclear magnetic resonance (NMR)methods.

[0052] Referring now to the Drawings, FIG. 2 illustrates the NMR spectraof the silicate medium before treating zinc components and FIG. 3illustrates the NMR spectra of the silicate medium following zinccomponent treatment. FIGS. 2 and 3 include the spectral trace,integrated peak areas and individual peak data. The relative amounts ofdifferent Si—O linkages in a sample are determined by comparing theintegrated peak areas.

[0053] In each of the spectra there is a series of S-shaped curvesassociated with a number. For example, in the spectrum of FIG. 2, theintegrated peak area for the −72.25 ppm peak (assigned to Q⁰, monomer)is 10.00. There is also a series of S-shaped curves ranging from about−86 ppm to −130 ppm which include three types of linkages. In order toobtain the integrated area for polymer, Q⁴, it was necessary to subtractthe integrated areas for the other two linkage types. Thus theintegrated area for polymer in this sample is 144.0242.01−29.61−=72.2.The following table summarizes the integrated peak area data. Integrated% Linkage Integrated % Linkage Area-used Type-used Area-new Type-newLinkage Type medium medium medium medium Q⁰, monomer 10.0 6.0 10.0 6.6Q¹, end groups and Q² _(cy3), middle 3-ring groups 12.44 7.5 13.35 8.9Q² _(lin), Q² _(cy4), middle linear and 4-ring groups, 29.61 17.8 31.7121.1 Q³ _(cy3), branching 3-ring groups Q³ _(cy4), branching 4-ringgroups 42.01 25.3 44.54 29.6 Q⁴ polymer 72.2 43.4 50.76 33.7 Sum ofintegrated intensities 166.26 150.36

[0054] A description of the different linkage types is found inEngelhardt and Michel, “High Resolution Solid State NMR of Silicates andZeolites, p. 76; hereby incorporated by reference.

[0055] The data show that the used sample has more polymer and less ofthe smaller anions than the new sample. The data also show that Q0 andQ1 species are more actively involved in an interaction or a reactionwith the zinc surfaces (Q0 can react with zinc to form willimite and Q1can react with zinc to form hemimorphite type of zinc disilicate).

Example 2

[0056] This Example demonstrates treating the silicate medium prior tocontacting metal surfaces in order to obtain a medium having desirablesilicate oligimers and using the treated medium to form a mineral-likesilicate layer.

[0057] The silicate medium was treated by placing an inert anode andinert cathode in an inert fixture. Specifically, platinum clad niobiumpanels of substantially the same dimensions were used for both the anodeand the cathode. The fixture was fabricated from polyproplyene andinstalled in a 4 liter beaker set on a hot plate. A parastolic pump wasused to transfer the treated silicate medium (e.g., at least partiallydepolymerized sodium silicate) to a second beaker. The second beaker wasused to expose zinc plated parts to the cathodic process described inU.S. patent application Ser. No. 09/814,641; hereby incorporated byreference. The second bath was also placed on a hot plate. Both bathswere maintained at 80° C.

[0058] The process was run in both sodium silicate as well as potassiumsilicate with varied sodium to silica oxide ratios.

[0059] The corrosion resistance of parts processed in accordance withthe above process were tested by neutral salt fog testing per ASTM B117.The corrosion resistance was increased from 24 hours (formation of firstwhite rust corrosion) to 48 hours.

Example 3

[0060] This Example illustrates a barrel apparatus that can be used fortreating metal parts in a bipolar silicate medium. Referring now to thedrawings, FIG. 4 illustrates a process barrel that is constructed frommaterials known in the zinc plating art (e.g., polypropylene). Theprocess barrel is at least partially filled with metallic parts such asrivets, fasteners, among other components conventionally used in barrelmetal finishing, and then inserted into a process tank containing asilicate medium. A dimensionally stable anode (e.g., constructed fromplatinum plated niobium mesh) is located between the process barrel andthe sides of the process tank. The anode and process barrel areconnected to a commercially available rectifier in a manner such that acylindrical mesh located about the center longitudinal axis of thebarrel functions as a cathode. A non-conductive mesh is locatedconcentrically about the cathode mesh in order to allow contact betweenthe cathode mesh and the silicate medium while preventing parts fromcontacting the cathode mesh (e.g., during rotation of the barrel). Whenpower is supplied to the barrel, anode and cathode, the metal parts arerotated within a bipolar silicate medium.

Example 4

[0061] This Examples demonstrates a bipolar process for treating zincplated tubular metal rivets. The rivets measured about 0.75 inch byabout 1.0 inch. The rivets were pretreated or cleaned by:

[0062] 1) washing with soap and water,

[0063] 2) agitate within 0.5% nitric acid at room temperature for 30seconds,

[0064] 3) rinse for 10 seconds in de-ionized water,

[0065] 4) agitate within 38% NaOH at 75C for 30 seconds,

[0066] 5) rinse with 10 seconds with warm tap water.

[0067] A silicate medium was established by adding 10 vol % N-gradesodium silicate to a bath heated to 75C. The bath measured about 4 byabout 4 inches. An anode and cathode each comprising 3×6 inchdimensionally stable mesh panels were inserted into the bath. Thepretreated rivets were placed in a polyproplyene and immersed in thesilicate medium. Current was supplied to the anode and cathode at about7-9A which achieved a current density of about 0.5 ASI at 15V. Therivets were maintained in the silicate medium for about 15 minutes. Therivets were dried under atmospheric conditions in a furnace at 80C for 4minutes. The dried rivets were rinsed with tap water for 10 seconds andoven dried again.

Example 5

[0068] Example 4 was repeated except that the silicate medium wastreated with electricity for 15 minutes at 0.5 ASI in accordance withExample 2 prior to introducing the rivets. The rivets were immersedwithin the treated silicate medium having a temperature of about 80C fora period of about 2 minutes.

Examples 6-10

[0069] These examples demonstrate applying a topcoat upon articlestreated in accordance with the inventive process. The articles comprisedzinc plated rivets measuring ⅛ inch tubular shank with a ¾ inch dia.head, and the topcoat comprised a black cathodic lacquer (availablecommercially as PPG Black Powerseal XL). Prior to conducting theinventive process, the articles were chemically darkened by exposure toone of the following processes: ammonium molybdate rinse, commerciallyavailable solution (e.g., Insta-Blak Z-360), and anodization. Forpurposes of comparison, zinc plated rivets, which were not processed inaccordance with the inventive process, were coated with the cathodiclacquer. The corrosion performance of all rivets was tested inaccordance with ASTM B-119 and the first occurrence of white rust (zinccorrosion products) was recorded (in general a relatively long period oftesting time before occurrence of white rust corresponds to a morecorrosion resistance article). The average first white rust for thecontrol or comparison rivets was 538 hours.

[0070] The following Examples list each step of the Process that wasused to treat the rivets and the length of time for each Process.

Example 6

[0071] Process Time A. Pretreat - Soap and Water (Clean) 1.0 Min. Rinse(3X)  10 Sec/Each B. Activate - .01% Sulfuric Acid  30 Sec Rinse (3X) 10 Sec/Each C. Blacken - 12 g/l Ammonium Molybdate  45 Min 5 m/lAmmonia D. Dry - Spin Dry E. Silicate Medium - 10% N Grade SodiumSilicate Solution/D.I. Water @ 75° C. pH 11.07, SG = 1.047 ElectrifyMedium with 7-9 Amp  15 Min. @ 15.7 Volts - Shut Off Power Then DropWorkpiece Into Medium and Rotate Barrel   2 Min F. Drying - None G.Topcoat - PPG Cathodic Black Lacquer

[0072] ASTM B-117 Performance: First White Rust 864 hours

Example 7

[0073] Process Time A. Pretreat - E-Kleen 148 Solution (500 ml) 30 Sec@37° C. Rinse (3X) 10 Sec/Each B. Activate - E-Kleen 154 Solution 30 Sec@ Ambient Rinse (3X) 10 Sec/Each C. Blacken - Insta-Blak Z-360  5 MinRinse  5 Min D. Silicate Medium - 10% N Grade Sodium SilicateSolution/D.I. Water @ 75° C. pH 11.07, SG = 1.047 Electrify Medium With15 Min 7-9 Amp @ 15.7 Volts Shut Off Power And Then Drop Workpiece intoMedium Rotate Barrel  2 Min E. Drying - 120° C.  4 Min F. Topcoat - PPGCathodic Black Lacquer

[0074] ASTM B-117 Performance: First White Rust 504 hours

Example 8

[0075] Process Time A. Pretreat - Soap and Water (Clean) 1.0 Min Rinse(3X)  10 Sec/Each B. Activate - 1% Sulfuric Acid  30 Sec C. Blacken -Anodize in NaOH (60 g/l  30 Min @ 35-40° C. @ 1.2 Amps, 3 Volts D. Dry -Spin Dry  30 Sec E. Silicate Medium - 17.5% D Grade Sodium SilicateSolution/D.I. Water @ 75° C., pH 11.84, Electrify Medium with  15 Min1.1 Amps, 2 Volts Shut Off Power Drop Work Piece Into Medium RotateBarrel   2 Min F. Drying - 80° C.   4 Min G. Topcoat - P.P.G. CathodicBlack Lacquer

[0076] ASTM B-117 Performance: First White Rust 826 hours

Example 9

[0077] Process Time A. Pretreat - Soap and Water (Clean)  1 Min Rinse(3X) 10 Sec/Each B. Activate - 0.1% Sulfuric Acid 30 Sec Rinse (3X) 10Sec/Each C. Blacken - 12 g/l Ammonium Molybdate 45 Sec And 5 ml AmmoniaD. Dry - Spin Dry 30 Sec E. Silicate Medium - 10% N Grade SodiumSilicate/D.I. Water S.G. 1.044 Electrify Medium 15 Min @ 75° C., 7-8Amp, 15.7 Volts Shut Off Power Drop Workpiece Into Bath Rotate Barrel  2Min F. Drying - 4 Min @ 120° C. G. Topcoat - P.P.G. Cathodic BlackLacquer

[0078] ASTM B-177 Performance: First White Rust 522 hours

Example 10

[0079] Process Time A. Pretreat - Soap and Watr (Clean)  1 Min Rinse(3X) 10 Sec/Each B. Activate - 0.1% Sulfuric Acid 30 Sec Rinse (3X) 10Sec/Each C. Blacken - Anodize in NaOH (60 g/l @ 30 Min 35-40° C.) @ 1.2Amps, 3 Volts D. Dry - Spin Dry 30 Sec E. Silicate Medium - 10% N GradeSodium Silicate/D.I. Water S.G. 1.044, Electrify Medium 15 Min @ 75° C.,7-8 Amp, 15.7 Volts Shut Off Power Drop Workpiece Into Medium RotateBarrel.  2 Min F. Dry - None G. Topcoat - P.P.G. Cathodic Black Lacquer

[0080] ASTM B-117 Performance: First White Rust 828 hours

[0081] Examples 6-10 illustrate that, in some cases, the instantinvention can be employed along with a blackening or darkeningpretreatment for improving the corrosion resistance of topcoatedarticles as well as achieving a substantially uniform black with onecoat of lacquer

Example 11

[0082] Example 4 was repeated with the exception that the rivets wereexposed to a metal pretreatment prior to being introduced into thesilicate medium. The metal pretreatment comprised dipping the rivetsinto a solution comprising sodium silicate, magnesium and aluminum(e.g., available commercially as RP-90 from A-Brite Company, Dallas,Tex.), and spin drying. The pretreated rivets were then exposed to thesilicate medium for a period of about 7.5 minutes while applying acathodic current to rivets. The rivets were dried, rinsed and dried inaccordance with Example 4. The corrosion resistance of the dried rivetswas tested in accordance with ASTM B-117 and achieved an average of 192hours before the first occurrence of white rust (zinc corrosionproducts).

Example 12

[0083] Example 11 was repeated with the exception that the metalpretreatment was thickened by adding an aliphatic polymer withcarboxylic acid groups (CARBOPOL supplied by B.F. Goodrich), and theelectrolytic treatment in the silicate medium was for 3.5 minutes. Thecorrosion resistance of the dried rivets was tested in accordance withASTM B-117 and achieved an average of 234 hours before the firstoccurrence of white rust (zinc corrosion products).

Example 13

[0084] Example 11 was repeated with the exception that the metalpretreatment comprised sodium aluminate, sodium hydroxide and water (20ml of 5 wt. % sodium hydroxide and 14 grams of sodium aluminate), andthe electrolytic treatment in the silicate medium was for 3.5 minutes.The corrosion resistance of the dried rivets was tested in accordancewith ASTM B-117 and achieved an average of 373 hours before the firstoccurrence of white rust (zinc corrosion products).

Example 14

[0085] In this Example, Example 4 was repeated with the exception thatthe rivets were not pretreated/cleaned and were exposed to an acidicpost-treatment. Rivets were treated with the process of Example 4 for aperiod of thirty (30) seconds, spun dry, rinsed in deionized water andthen immersed in each of the following dilute acidic solutions: Citricacid (pH 2.2, 5 ml acid in 200 ml deionized water), oxalic acid (pH 3.0,5 ml oxalic acid and 200 ml deionized water) and glacial acetic acid (pH3.4, 5 ml glacial acetic acid and 2 liters deionized water). Thecorrosion resistance of the acid treated rivets was tested in accordancewith ASTM B-117 and the following number of hours passed without theappearance of white rust (zinc corrosion products): citric =72 hrs,oxalic =24 hrs and glacial acetic acid =72 hrs.

Example 15

[0086] This Example demonstrates using the inventive process as apost-treatment for the electrolytic process described in theaforementioned Cross Referenced Related Patents and Patent Applications.The rivets of Example 4 were cleaned with soap and water and then dippedin dilute nitric acid. The rivets were then introduced into a silicatemedium of Example 4 and a charge ranging from 7 to 9 amps at 15.7 V wasapplied with the rivets corresponding to the cathode. The current wasdisconnected and the rivets were removed from the silicate medium, andthen reintroduced into the silicate medium for a period of 15 minutes(without current being applied). The rivets were dried for 4 minutes at80C, rinsed in deionized water and dried again. The corrosion resistanceof the dried rivets was tested in accordance with ASTM B-117 andachieved an average of 160 hours before the first occurrence of whiterust (zinc corrosion products).

Example 16

[0087] This Example demonstrates using a pretreatment and apost-treatment for the inventive process. The rivets of Example 4 werecleaned in soap and water and rinsed three times in deionized water. Therinsed rivets were then dipped three times in dilute nitric acid andrinsed three times in deionized water. The rinsed rivets were thenpretreated by being immersed in sodium aluminate (38% sodium aluminateliquid [supplied by UALCO],10;1 dilution with deionized water). Thepretreated rivets were then spun dry. The dried rivets were then treatedin accordance with Example 4 but with a bath comprising sodium silicatehaving a 6:1 alkaline to silicate ratio (D Grade sodium silicate from PQCorporation). The rivets were then spun dry for 2 minutes at atemperature of 120F. The dried rivets were then immersed in a solutioncomprising colloidal silica (10 wt. % Ludox CL). The rivets were thendried for 2 minutes at a temperature of 120F. A secondary coating orsealer comprising silicate (RP 90 supplied by A Brite) was applied ontothe dried rivets. The rivets were dried for 3 minutes at 65 C. Thecorrosion resistance of the dried rivets was tested in accordance withASTM B-117 and achieved an average of 188 hours before the firstoccurrence of white rust (zinc corrosion products).

Example 17

[0088] This example demonstrates using a pretreatment prior to exposureto a silicate bath of the instant invention. Rivets were pretreated inaccordance with the description set forth in following Tables 1 and 2.The sodium silicate bath of Example 4 was electrified prior tointroducing the pretreated rivets. The corrosion resistance of therivets was tested in accordance with ASTM B-117. The resistance of therivets to white rust (zinc corrosion products) is set forth in Table 1,and the resistance of the rivets to the formation of red rust(underlying iron corrosion) is set forth in Table 2. TABLE 1 IDDescription Max Min Average Std. Dev CV Range SAMPLE 1 Group A1 SodiumAcetate, 0.001 wt % 72 48 60 12.8 0.21 24 48 Group A2 Sodium Acetate,0.5 wt % 96 24 48 22.2 0.46 72 48 Group A3 Sodium Acetate, 5.0 wt % 9648 66 17.0 0.26 48 48 Group B1 Aluminum Ammonium Sulfate, 0.001 wt % 7248 51 8.5 0.17 24 48 Group B2 Aluminum Ammonium Sulfate, 0.5 wt % 48 2442 11.1 0.26 24 48 Group B3 Aluminum Ammonium Sulfate, 5.0 wt % 120 2454 30.8 0.57 96 48 Group C1 Aluminum Phosphate, 0.001 wt % 72 24 51 20.00.39 48 48 Group C2 Aluminum Phosphate, 0.5 wt % 96 24 60 22.2 0.37 7272 Group C3 Aluminum Phosphate, 5.0 wt % 144 48 78 33.3 0.43 96 48 GroupD1 Aluminum Nitrate, 0.001 wt % 72 24 51 15.4 0.30 48 72 Group D2Aluminum Nitrate, 0.5 wt % 72 24 33 17.9 0.54 48 24 Group D3 AluminumNitrate, 5.0 wt % 48 24 33 12.4 0.38 24 24 Group E1 Aluminum Fluoride,0.001 wt % 72 24 57 17.9 0.31 48 48 Group E2 Aluminum Fluoride, 0.5 wt %48 24 42 11.1 0.26 24 48 Group E3 Aluminum Fluoride, 5.0 wt % 48 24 3312.4 0.38 24 24 Group F1 Zn(a)/Pretreat/SP0.5/DRD Control for A-E 72 2451 20.0 0.39 48 24 Group F2 Zn(a)/SP0.5/DRD Only 96 48 66 17.0 0.26 4872 Group F3 Zinc Plate(a) Only Control 24 24 24 0.0 0.00 0 24 Group G1Pretreat/0.001 wt % Al K Sulfate/Sp0.5 DRD 72 24 51 15.4 0.30 48 48Group G2 Pretreat/0.5 wt % Al K Sulfate/Sp0.5 DRD 96 24 57 22.0 0.39 7224 Group G3 Pretreat/5.0 wt % Al K Sulfate/Sp0.5 DRD 72 24 57 17.9 0.3148 72 Group G4 Pretreat/SP0.5/D/5.0 wt % Al K Sulfate/D 48 24 39 12.40.32 24 48 Group H1 Pretreat/0.001 wt % Al Tartrate/SP0.5 DRD 48 24 3912.4 0.32 24 48 Group H2 Pretreat/0.5 wt % Al Tartrate/SP0.5 DRD 72 2445 15.4 0.34 48 48 Group H3 Pretreat/5.0 wt % Al Tartrate/SP0.5 DRD 4824 30 11.1 0.37 24 24 Group I1 Pretreat/0.001 wt % NaNH4PO4/SP0.5 DRD 4824 39 12.4 0.32 24 48 Group I2 Pretreat/0.5 wt % NaNH4PO4/SP0.5 DRD 7224 48 18.1 0.38 48 24 Group I3 Pretreat/5.0 wt % NaNH4PO4/SP0.5 DRD 7224 45 15.4 0.34 48 48 Group J1 Pretreat/0.001 wt % Na D Gluconate/SP0.5DRD 72 24 48 12.8 0.27 48 24 Group J2 Pretreat/0.5 wt % Na DGluconate/SP0.5 DRD 72 24 48 18.1 0.38 48 48 Group J3 Pretreat/5.0 wt %Na D Gluconate/SP0.5 DRD 96 48 63 17.9 0.28 48 48 Group K1Zn(a)/Pretreat/SP0.5 DRD 96 24 48 22.2 0.46 72 48 Group K2Zn(b)/Pretreat/SP0.5 DRD Control For G-K 96 24 54 21.3 0.39 72 48 GroupK3 Zn(b)SP 0.5 DRD only 144 48 72 38.5 0.53 96 48 Group K4 Zn(b) ZincPlate Only 24 24 24 0.0 0.00 0 24 Group K5 SP 0.5 D/pH 3.4 Acetic Acid/D72 48 51 8.5 0.17 24 48 ID SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 SAMPLE 6SAMPLE 7 SAMPLE 8 Group A1 72 48 48 72 72 72 48 Group A2 48 24 96 48 4848 24 Group A3 48 48 96 72 72 72 72 Group B1 48 48 48 48 48 72 48 GroupB2 24 48 48 48 48 48 24 Group B3 48 24 72 24 48 48 120 Group C1 48 72 7224 24 48 72 Group C2 96 48 24 72 72 48 48 Group C3 72 48 48 96 72 96 144Group D1 48 24 48 48 48 48 72 Group D2 24 24 24 24 24 48 72 Group D3 2424 24 24 48 48 48 Group E1 24 48 72 48 72 72 72 Group E2 48 48 48 48 4824 24 Group E3 48 48 24 48 24 24 24 Group F1 24 48 72 48 72 48 72 GroupF2 48 48 72 48 72 96 72 Group F3 24 24 24 24 24 24 24 Group G1 48 48 7224 48 48 72 Group G2 72 48 72 48 48 48 96 Group G3 72 48 72 24 72 48 48Group G4 48 48 48 48 24 24 24 Group H1 48 24 48 48 48 24 24 Group H2 2448 48 72 48 24 48 Group H3 24 48 24 24 24 48 24 Group I1 48 24 48 48 2424 48 Group I2 48 48 24 48 48 24 24 Group I3 48 72 24 24 48 48 48 GroupJ1 48 48 72 48 48 48 48 Group J2 24 48 72 24 72 48 48 Group J3 96 72 4872 48 72 48 Group K1 48 96 24 24 48 48 48 Group K2 48 96 24 48 48 72 48Group K3 48 48 72 48 120 144 48 Group K4 24 24 24 24 24 24 24 Group K548 48 48 48 48 48 72

[0089] TABLE 2 ID Description Max Min Average Range St. Dev. CV SAMPLE 1Group A1 Sodium Acetate, 0.001 wt % 168 96 135 72.0 22.0 0.16 120 GroupA2 Sodium Acetate, 0.5 wt % 168 120 135 48.0 22.0 0.16 120 Group A3Sodium Acetate, 5.0 wt % 168 96 138 72.0 24.8 0.18 96 Group B1 AluminumAmmonium Sulfate, 0.001 wt % 144 96 111 48.0 17.9 0.16 96 Group B2Aluminum Ammonium Sulfate, 0.5 wt % 144 96 114 48.0 17.0 0.15 96 GroupB3 Aluminum Ammonium Sulfate, 5.0 wt % 144 72 111 72.0 25.5 0.23 72Group C1 Aluminum Phosphate, 0.001 wt % 144 96 126 48.0 21.3 0.17 120Group C2 Aluminum Phosphate, 0.5 wt % 144 120 123 24.0 8.5 0.07 120Group C3 Aluminum Phosphate, 5.0 wt % 168 96 132 72.0 25.7 0.19 96 GroupD1 Aluminum Nitrate, 0.001 wt % 168 120 135 48.0 17.9 0.13 120 Group D2Aluminum Nitrate, 0.5 wt % 144 96 108 48.0 18.1 0.17 96 Group D3Aluminum Nitrate, 5.0 wt % 144 96 114 48.0 17.0 0.15 96 Group E1Aluminum Fluoride, 0.001 wt % 144 120 123 24.0 8.5 0.07 120 Group E2Aluminum Fluoride, 0.5 wt % 144 96 111 48.0 17.9 0.16 120 Group E3Aluminum Fluoride, 5.0 wt % 120 96 108 24.0 12.8 0.12 96 Group F1Zn(a)/Pretreat/SP0.5/DRD Control for A-E 144 120 129 48.0 12.4 0.10 120Group F2 Zn(a)/SP0.5/DRD Only 168 144 153 24.0 12.4 0.08 144 Group F3Zinc Plate(a) Only Control 72 48 60 24.0 12.8 0.21 48 Group G1Pretreat/0.001 wt % Al K Sulfate/Sp0.5 DRD 216 168 192 48.0 12.8 0.07192 Group G2 Pretreat/0.5 wt % Al K Sulfate/Sp0.5 DRD 216 168 198 48.017.0 0.09 168 Group G3 Pretreat/5.0 wt % Al K Sulfate/Sp0.5 DRD 240 168195 72.0 27.0 0.14 240 Group G4 Pretreat/SP0.5/D/5.0 wt % Al K Sulfate/D216 168 189 48.0 20.0 0.11 168 Group H1 Pretreat/0.001 wt % AlTartrate/SP0.5 DRD 168 96 126 72.0 28.0 0.22 168 Group H2 Pretreat/0.5wt % Al Tartrate/SP0.5 DRD 240 168 189 72.0 23.8 0.13 192 Group H3Pretreat/5.0 wt % Al Tartrate/SP0.5 DRD 216 120 177 96.0 33.8 0.19 168Group I1 Pretreat/0.001 wt % NaNH4PO4/SP0.5 DRD 216 144 180 72.0 22.20.12 216 Group I2 Pretreat/0.5 wt % NaNH4PO4/SP0.5 DRD 216 168 198 48.017.0 0.09 216 Group I3 Pretreat/5.0 wt % NaNH4PO4/SP0.5 DRD 192 168 18024.0 12.8 0.07 192 Group J1 Pretreat/0.001 wt % Na D Gluconate/SP0.5 DRD192 144 165 48.0 20.0 0.12 192 Group J2 Pretreat/0.5 wt % Na DGluconate/SP0.5 DRD 216 168 198 48.0 17.0 0.09 216 Group J3 Pretreat/5.0wt % Na D Gluconate/SP0.5 DRD 264 192 219 72.0 23.8 0.11 192 Group K1Zn(a)/Pretreat//SP0.5 DRD 216 120 156 96.0 28.7 0.18 144 Group K2Zn(b)/Pretreat//SP0.5 DRD Control For G-K 240 192 222 48.0 24.8 0.11 192Group K3 Zn(b)SP 0.5 DRD only 288 168 219 120.0 39.4 0.18 216 Group K4Zn(b) Zinc Plate Only 144 96 123 48.0 15.4 0.13 120 Group K5 SP 0.5 D/pH3.4 Acetic Acid/D 216 168 201 48.0 17.9 0.09 216 ID SAMPLE 2 SAMPLE 3SAMPLE 4 SAMPLE 5 SAMPLE 6 SAMPLE 7 SAMPLE 8 Group A1 144 96 120 144 144168 144 Group A2 120 120 168 144 120 168 120 Group A3 120 120 168 144144 144 168 Group B1 96 96 120 120 96 144 120 Group B2 96 120 120 144120 120 96 Group B3 96 96 120 96 120 144 144 Group C1 96 144 144 96 144120 144 Group C2 120 120 120 120 144 120 120 Group C3 120 120 120 144120 168 168 Group D1 120 120 168 144 120 144 144 Group D2 96 120 96 9696 120 144 Group D3 96 96 120 120 120 120 144 Group E1 120 120 120 120120 120 144 Group E2 120 120 96 96 96 96 144 Group E3 96 120 120 120 12096 96 Group F1 120 120 144 120 144 120 144 Group F2 144 144 144 168 144168 168 Group F3 72 48 72 72 48 48 72 Group G1 216 192 192 192 168 192192 Group G2 192 192 216 216 216 192 192 Group G3 192 192 216 168 216168 168 Group G4 216 192 192 192 168 168 216 Group H1 144 96 96 144 144120 96 Group H2 192 168 168 240 192 168 192 Group H3 168 216 144 120 216192 192 Group I1 192 168 168 192 168 144 192 Group I2 192 192 216 192216 168 192 Group I3 192 192 168 168 168 168 192 Group J1 168 144 144168 144 168 192 Group J2 192 192 216 192 216 168 192 Group J3 264 216216 240 216 216 192 Group K1 144 216 120 168 168 144 144 Group K2 240240 240 240 192 240 192 Group K3 216 192 216 192 264 288 168 Group K4144 96 144 120 120 120 120 Group K5 168 216 216 192 216 192 192

[0090] While the apparatus, compositions and methods of this inventionhave been described herein, it will be apparent to those of skill in theart that variations may be applied to the process described hereinwithout departing from the concept and scope of the invention. All suchsimilar substitutes and modifications apparent to those skilled in theart are deemed to be within the scope and concept of the invention andthe appended claims.

The following is claimed:
 1. A method for treating a substrate having anelectrically conductive surface comprising: preparing a mediumcomprising water and at least one silicate and wherein the medium has abasic pH, passing a current through the medium and then; contacting atleast a portion of the surface with the medium.
 2. The method of claim 1wherein the medium further comprises colloidal silica, and wherein themedium is substantially free of chromates and VOCs.
 3. A method fortreating a metallic or an electrically conductive surface comprising:preparing a medium comprising water and at least one silicate andwherein the medium has a basic pH, placing an anode and a cathode inelectrical contact with the medium, exposing at least a portion of thesurface to a medium, passing a current through the medium wherein thesurface is not in direct contact with the anode or cathode.
 4. Themethod of claim 3 wherein the colloidal silica has a particle size ofless than about 50 nanometers.
 5. The method of claim 1 wherein thesurface comprises at least one member selected from the group consistingof copper, nickel, tin, iron, zinc, aluminum, magnesium, stainless steeland steel and alloys thereof.
 6. The method of claim 1 furthercomprising drying and rinsing and said rinsing comprises contacting thesurface with a second medium comprising a combination comprising waterand at least one water soluble compound selected from the groupconsisting of carbonates, chlorides, fluorides, nitrates, zironates,titanates, sulphates, water soluble lithium compounds and silanes. 7.The method of claim 1 wherein the medium comprises at least one dopantselected from the group consisting of zinc, cobalt, molybdenum, nickeland aluminum.
 8. The method of claim 6 wherein said drying is conductedat a temperature of at least about 120C.
 9. The method of claim 5wherein said surface comprises zinc or zinc alloys.
 10. The method ofclaim 1 wherein said surface comprises a chromated surface.
 11. Themethod of claim 3 wherein the surface comprises a chromated surface. 12.The method of claim 3 wherein said medium further comprises at least onewater dispersible polymer.
 13. The method of claim 1 wherein said methodfurther comprises contacting with at least one acid.
 14. The method ofclaim 9 wherein said surface comprises zinc nickel alloys.
 15. Themethod of claim 1 further comprising pretreating the surface prior tosaid contacting.
 16. The method of claim 1 further comprising applyingat least one coating selected from the group consisting of latex,silanes, epoxies, silicone, amines, alkyds, urethanes, polyester andacrylics.
 17. The method of claim 15 wherein the pretreating comprisescontacting the surface with at least one member selected from the groupconsisting of sodium acetate, aluminum ammonium sulfate, aluminumphosphate, aluminum nitrate, aluminum fluoride, aluminum potassiumsulfate, aluminum tartate, sodium ammonium phosphate and sodiumgluconate.